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Microcontroller logic high and low settings...help!!

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x2pher

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Hi Guys,
Please help..!

I have attached the circuit. I have difficulty on how to set microcontroller P3.3 and P3.4 into high and low state:

There are only 2 condition:

(1) If I short SO pin 1 and 2 .. I need low (0V) at P3.3 while the P3.4 is high (5V or 3.3V)

(1) If I short SO pin 3 and 4 .. I need low (0V) at P3.4 while the P3.3 is high (5V or 3.3V)


Problem:
1.0 On the current circuit, Q14 cannot turn on; P3.3 and P3.4 is always high.
2.0 Changing R15 and R16 to 4ohms resistor shuts the 5V down.


Please help!!
 

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betwixt

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Thos values are completely wrong. The reason it doesn't work is the current flowing through the transistors is far too high and is pulling the supply voltage down.

Change the resistors on SO 1 and 3 to 47K Ohms
Change R17 and R18 to 10K Ohms.

You can completely remove the transistors, just connect SO between the logic inuts and ground, it will work exactly as before.

Brian.
 

btbass

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You don't say what micro you are using?
Your circuit doesn't look right?

C4 should decouple the supply and have + to the 5V and - direct to ground.
R22 should go from +5v to RST.

R17 and R18 are far to low a value?
10K would be better.
 

Senthilkumar_rjpm

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What is the purpose you are using this circuit... Why you made SO in this circuit... you can give gnd directly to micro (jus replace 30ohms to higher value >2.2k upto 50k)... Do you taking SO points from some other circuit? pls proide more details
 

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